I have this cosmetic issue with reading rpm from the spindle vfd via modbus. Im using 2 pole motor and setting Hz values, so 400Hz is 24000rpm. Vfd expects the Hz value multiplied by 100, so 40000 means 400.00 Hz. It looks like the change to negative value happens at exactly 32768 (2^15 binary number)
Is there any way to fix this?

I was able to find out, that there is an option to set signed or unsigned register type in register definition.
This solved my issue.